In a water quality analysis device for analyzing a concentration of a specific component in sample water, in generally, a concentration of an analysis target component in sample water is obtained by injecting sample water into a reactor to cause a reaction corresponding to the analysis target component, sending a specific gas generated with this to a gas detection unit, and measuring its gas concentration, alternatively, by generating a specific ion in sample water by a reaction in a reactor, injecting the sample water after the reaction into a measuring cell of an absorption spectrometer, and measuring the ion concentration (see, for example, Patent Document 1).
In such an analysis device, usually, after completion of one analysis, wash water (generally pure water used as dilution water) is injected into a vessel such as a reactor or a measuring cell into which sample water is injected, and discharged under prescribed procedures to automatically clean the inside of the vessel so that the previous sample water does not affect the subsequent analysis (see, for example, Patent Document 2).